Cross-sectional areas of gas ducts along which gaseous fluids are conveyed, are known to greatly increase with evergrowing unit power of plants and arrangements made use of in power engineering, metallurgy, and some other fields of engineering.
One prior-art shutoff device for closing a large-area gas duct is known to be of the flapper type and to comprise a housing, a closing element with a mechanical actuator, and a sealing seat. The closing element is made as a heavy disk- or plate-shaped flapper (cf. journal "Gas Turbine World", March 1976, p. 53).
Increasing the size of such closing elements would increase their weight and involve difficulties in providing gas-tightness and heat insulation of the gas duct segments being shut off; this, in turn, necessitates the application of a mechanical actuator capable of developing considerable forces required to operate such shutoff devices, as well as the provision of some additional elements and contrivances in the construction of such shutoff devices, adapted to damp the stroke of said element against the sealing seat and to improve gas tightness of said devices.
Another shutoff device is known (cf. USSR Inventor's Certificate No. 567,896 cl.F23L 13/02, issued 1974) to comprise two gate elements mounted pivotally from the vertical position through 90.degree. to the opposite sides. When in the vertical position said gate elements establish, along with the gas duct walls, a lock chamber provided in its top portion with an engorgement to be filled with a loose refractory materials.
The afore-discussed construction arrangement of the shutoff device, when applied to close a large cross-sectional area gas duct, involves the employment of a mechanical actuator capable of developing great forces on account of heavyweight gate elements said actuator is to operate. The loose material filling the lock chamber tends to thrust out the gate elements and is liable to run down through the resultant gap, thus deteriorating the tightness of the gas-duct segment being shut off.
One more shutoff device for closing a large-area gas duct, assumed by us as the prototype, is known to comprise a housing, a closing element shaped as a louvre grill, wherein the louvres can swivel round their pivot pins from a mechanical actuator provided on the housing (cf. French Patent No. 2,169,330 issued Oct. 12, 1973, class F24f 13/14).
Increased overall size of the closing device made as a louvre grill and applied to shut off a large-area gas duct, causes higher leaks of the fluid handled through said closing device, owing to the fact that large-sized grill louvres cannot be fitted tightly against one another, which results also in considerable heat losses to the surrounding atmosphere.
It is an aobject of the present invention to provide a shutoff device of the louvre type, making it possible to eliminate leaks of the gaseous fluids being handled through the closing element.
It is another object of the present invention to provide a shutoff device of the louvre type, which makes it possible to reduce heat losses to the surrounding atmosphere.
It is one more object of the present invention to eliminate hanging-up of the sealing loose material in the lock chamber.